<div style="text-align:right;">
  <form id="loginform" action="" method="post" onsubmit="return loginFormSubmit()">
    <label><em>Username : </em><input type="text" id="username" name="username" class="input"/></label><br />
    <label><em>Password : </em><input type="password" id="password" name="password" class="input"/></label><br />
    <input type="submit" class="button alignright" name="submit" id="submit" value="Login" style="margin: 0;"/>
  </form>
</div>

<script type="text/javascript">

    var loginFormSubmit = function(){
        var instance = ZweBox.getInstance();

        if(document.id('username').get('value') == 'zwebox' && document.id('password').get('value') == 'zwebox')
            instance.shake('top');
        else
            instance.shake();

        return false;
    };

</script>